Abstract
The present study deals with the lithostratigraphy, biostratigraphy and chronostratigraphy of the Eocene- Oligocene boundary in three surface sections in Sinjar anticline, northwestern Iraq. Jaddala Formation composed of marl, marly limestone represents deep Eocene facies, Palani, and Tarjil formations represent Early and Late Oligocene sequences. Sixty-two planktonic foraminiferal species belonging to sixteen genera have been recognized which permit the recognition of four Zones; these are from older at the base: Globorotalia opima opima Total- Range Zone (P21) Globigerina ampliapertura partial- Range Zone (P20) Pseudohastigerina micra Interval Zone (P 19) Globigerinatheka subconglobata subconglobata Partial Range Zone (P11) (Part). The Eocene- Oligocene boundary in Sinjar area represents disconformity surface, where the deposition ceased in the Middle Eocene (Lutetian) at the end of Jaddala Formation, then deposition started at the Upper Early Oligocene due to rapid wide transgression, leading to the deposition of Palani (Rupelian) and Tarjil (Chatian) formations, which consist of thinly laminated hard white-pale brown intercalation of marly limestone and marl beds.
Highlights
The present study deals with the lithostratigraphy, biostratigraphy and chronostratigraphy of the Eocene- Oligocene boundary in three surface sections in Sinjar anticline, northwestern Iraq
The Eocene- Oligocene boundary in Sinjar area represents disconformity surface, where the deposition ceased in the Middle Eocene (Lutetian) at the end of Jaddala Formation, deposition started at the Upper Early Oligocene due to rapid wide transgression, leading to the deposition of Palani (Rupelian) and Tarjil (Chatian) formations, which consist of thinly laminated hard white-pale brown intercalation of marly limestone and marl beds
The purpose of this paper is: (1) to give a detailed lithological description to the exposed studied sections of the Eocene-Oligocene boundary, which appears very clear in the study area due to the indications of discontinuity and erosion at the top of Jaddala Formation; and (2) to study the planktonic foraminiferal biostratigraphy through this boundary in order to give accurate age determination
Summary
The first description of Jaddala Formation was given by Henson in 1940 (Bellen et al, 1959), it’s type section lies near Jaddala village on the southern limb of Sinjar anticline, fifteen kilometers to the west of Sinjar city, northwestern Iraq. According to Al-Hashimi and Amer (1985), Palani Formation is known in the low folded and Mesopotamian zones, including typical basinal facies rich in plankton foraminifera, which may be condensed and reduced to few meters in northwestern Iraq. The purpose of this paper is: (1) to give a detailed lithological description to the exposed studied sections of the Eocene-Oligocene boundary, which appears very clear in the study area due to the indications of discontinuity and erosion at the top of Jaddala Formation; and (2) to study the planktonic foraminiferal biostratigraphy through this boundary in order to give accurate age determination
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